England hooker Dylan Hartley is set to have knee surgery on Tuesday that will rule him out of the rest of the Six Nations, his Northampton coach Chris Boyd said on Saturday.
Hartley, 32, is England's co-captain alongside fly-half Owen Farrell, but a knee injury has prevented him playing for club or country since before Christmas.
"Dylan went to see the surgeon and they felt in conjunction with our medical people the progress was a bit slow," Boyd was quoted as saying by the Northampton Chronicle.
"He's going to have a surgical procedure on Tuesday to open it up and see what's causing the knee to be grumbly. Depending on what they find, it will depend on how long his rehab will be.
"If it went outstandingly well, he could be playing in four weeks but if it's something a bit more problematic it might be a bit longer."
England's hopes of a Six Nations Grand Slam were dashed by Wales who beat them 21-13 in Cardiff on Saturday to move to the top of the standings.